Epidemiology of influenza virus infections in children with acute respiratory infections in Zambia

Facility-based surveillance for influenza and respiratory syncytial virus in rural Zambia

BACKGROUND

While southern Africa experiences among the highest mortality rates from respiratory infections, the burden of influenza and respiratory syncytial virus (RSV) in rural areas is poorly understood.

METHODS

We implemented facility-based surveillance in Macha, Zambia. Outpatients and inpatients presenting with influenza-like illness (ILI) underwent testing for influenza A, influenza B, and RSV and were prospectively followed for 3 to 5 weeks to assess clinical course. Log-binomial models assessed correlates of infection and clinical severity.

RESULTS

Between December 2018 and December 2019, 17% of all outpatients presented with ILI and 16% of inpatients were admitted with an acute respiratory complaint. Influenza viruses and RSV were detected in 17% and 11% of outpatient participants with ILI, and 23% and 16% of inpatient participants with ILI, respectively. Influenza (July-September) and RSV (January-April) prevalence peaks were temporally distinct. RSV (relative risk [RR]: 1.78; 95% confidence interval [CI] 1.51-2.11), but not influenza, infection was associated with severe disease among patients with ILI. Underweight patients with ILI were more likely to be infected with influenza A (prevalence ratio [PR]: 1.72; 95% CI 1.04-2.87) and to have severe influenza A infections (RR: 2.49; 95% CI 1.57-3.93).

CONCLUSIONS

Populations in rural Zambia bear a sizeable burden of viral respiratory infections and severe disease. The epidemiology of infections in this rural area differs from that reported from urban areas in Zambia.

An evaluation of the Zambia influenza sentinel surveillance system, 2011-2017

Background

Over the past decade, influenza surveillance has been established in several African countries including Zambia. However, information on the on data quality and reliability of established influenza surveillance systems in Africa are limited. Such information would enable countries to assess the performance of their surveillance systems, identify shortfalls for improvement and provide evidence of data reliability for policy making and public health interventions.

Methods

We used the Centers for Disease Control and Prevention guidelines to evaluate the performance of the influenza surveillance system (ISS) in Zambia during 2011–2017 using 9 attributes: (i) data quality and completeness, (ii) timeliness, (iii) representativeness, (iv) flexibility, (v) simplicity, (vi) acceptability, (vii) stability, (viii) utility, and (ix) sustainability. Each attribute was evaluated using pre-defined indicators. For each indicator we obtained the proportion (expressed as percentage) of the outcome of interest over the total. A scale from 1 to 3 was used to provide a score for each attribute as follows: < 60% (as obtained in the calculation above) scored 1 (weak performance); 60–79% scored 2 (moderate performance); ≥80% scored 3 (good performance). An overall score for each attribute and the ISS was obtained by averaging the scores of all evaluated attributes.

Results

The overall mean score for the ISS in Zambia was 2.6. Key strengths of the system were the quality of data generated (score: 2.9), its flexibility (score: 3.0) especially to monitor viral pathogens other than influenza viruses, its simplicity (score: 2.8), acceptability (score: 3.0) and stability (score: 2.6) over the review period and its relatively low cost ($310,000 per annum). Identified weaknesses related mainly to geographic representativeness (score: 2.0), timeliness (score: 2.5), especially in shipment of samples from remote sites, and sustainability (score: 1.0) in the absence of external funds.

Conclusions

The system performed moderately well in our evaluation. Key improvements would include improvements in the timeliness of samples shipments and geographical coverage. However, these improvements would result in increased cost and logistical complexity. The ISSS in Zambia is largely reliant on external funds and the acceptability of maintaining the surveillance system through national funds would require evaluation.

Management of upper respiratory tract infections in children

Upper respiratory tract infection (URTI) occurs commonly in both children and adults and is a major cause of mild morbidity. It has a high cost to society, being responsible for absenteeism from school and work and unnecessary medical care, and is occasionally associated with serious sequelae. URTIs are usually caused by several families of virus; these are the rhinovirus, coronavirus, parainfluenza, respiratory syncytial virus (RSV), adenovirus, human metapneumovirus, influenza, enterovirus and the recently discovered bocavirus. This review will mainly focus on the rhinovirus, where significant advances have been made in understanding the epidemiology, natural history and relationship with other pathogens.

Influenza surveillance in Zambia, 2008-2009

BACKGROUND

Limited information exists about influenza viruses in Africa. We used data from a new sentinel surveillance system to investigate the seasonality and characteristics of influenza, including pandemic (pdm) influenza A H1N1, in Zambia.

METHODS

In June 2008, we established sentinel surveillance for influenza-like illness (ILI) and severe acute respiratory illness (SARI) at 4 healthcare facilities in Zambia. Nasopharyngeal and oropharyngeal swabs and structured questionnaires were collected from eligible patients and samples were tested by real-time reverse-transcription polymerase chain reaction for influenza virus types and subtypes.

RESULTS

From June 2008 to December 2009, we collected 1234 specimens, of which 334 (27%) were ILI, and 900 (63%) were SARI. Overall, 4% (57) of specimens were positive for influenza. The influenza detection rate in ILI and SARI cases was 5% (17/334) and 4% (40/900), respectively. Among all influenza cases, 54 (95%) were influenza A and 3 (5%) were influenza B. Of the influenza A viruses, 16 (30%) were A(H1N1)pdm09, 29 (54%) were seasonal A(H1N1), 6 (11%) were A(H3N2), and 4 (7%) were unsubtyped. The detection rate for A(H1N1)pdm09 cases was highest in persons aged 5-24 years (5/98; 5%), 25-44 years (4/78; 5%), and 45-64 years (1/17; 6%). Conversely, for seasonal influenza the detection rate was highest in children aged 1-4 years (18/294; 6%). Influenza virus circulation peaked during June-August in both years and A(H1N1)pdm09 occurred at the end of the influenza season in 2009.

CONCLUSIONS

Seasonal influenza virus infection was found to be associated with both mild and severe respiratory illness in Zambia. Future years of surveillance are necessary to better define the seasonality and epidemiology of influenza in the country.

Seasonal influenza epidemiology in sub-Saharan Africa: a systematic review

Acute respiratory infection (ARI) is a leading cause of mortality worldwide, of which influenza is an important cause that can be prevented with vaccination. We did a systematic review of research published from 1980 to 2009 on seasonal influenza epidemiology in sub-Saharan Africa to identify data strengths and weaknesses that might affect policy decisions, to assess the state of knowledge on influenza disease burden, and to ascertain unique features of influenza epidemiology in the region. We assessed 1203 papers, reviewed 104, and included 49 articles. 1-25% of outpatient ARI visits were caused by influenza (11 studies; mean 9·5%; median 10%), whereas 0·6-15·6% of children admitted to hospital for ARI had influenza identified (15 studies; mean 6·6%; median 6·3%). Influenza was highly seasonal in southern Africa. Other data were often absent, particularly direct measurement of influenza incidence rates for all ages, within different patient settings (outpatient, inpatient, community), and for all countries. Data from sub-Saharan Africa are insufficient to allow most countries to prioritise strategies for influenza prevention and control. Key data gaps include incidence and case-fatality ratios for all ages, the contribution of influenza towards admission of adults to hospital for ARI, representative seasonality data, economic burden, and the interaction of influenza with prevalent disorders in Africa, such as malaria, HIV, and malnutrition.

Enterovirus isolation from children with acute respiratory infections and presumptive identification by a modified microplate method

OBJECTIVE

To evaluate a modified microplate method, utilizing HEF, HEp-2, Vero, MDCK and newly introduced RD-18S and GMK cell lines, for virus isolation.

METHODS

From June to October 2001, 723 throat swab specimens taken from children with acute respiratory infections (ARIs) were inoculated onto these cells. To analyze cell sensitivity, we also inoculated 20 serotypes of stocked enteroviruses.

RESULTS

During the period, we isolated 40 Coxsackie A2 (CoxA2), 13 CoxA4, 16 CoxA16, 1 CoxB2, 11 CoxB3, 2 CoxB5, 54 echo16, 2 entero71 and 1 polio2. By observing a cell sensitivity pattern with HEF, HEp-2, Vero, RD-18S, and GMK, we could finally differentiate five enterovirus groups: CoxA except for CoxA16, CoxA16/entero71, CoxB, echovirus, and poliovirus.

CONCLUSIONS

With this system, the RD-18S cell line enabled us to isolate CoxA virus, except for CoxA16, for the first time. Differentiation of five enterovirus groups by cell sensitivity simplified the specific identification by neutralization test as a presumptive identification. A modified microplate method may be an appropriate cell combination for virus isolation, especially for enteroviruses, and is expected to be used routinely for virologic diagnosis and to clarify the epidemiology of ARI in children.